Reciprocatory piston type compressor for a refrigeration system

ABSTRACT

A reciprocatory piston type compressor having a cylinder block provided with a plurality of cylinder bores in which a refrigerant gas drawn from a suction chamber is compressed and discharged toward a discharge chamber from which the compressed refrigerant gas is delivered to a refrigeration system. The compressor further having an injection gas passageway for introducing a refrigerant gas at a relatively high pressure therein from a liquid-gas divider of the refrigeration system, and a rotary valve element rotated with a drive shaft of the compressor for equivalently injecting the high pressure refrigerant gas into every cylinder bore at a selected time and the compression of the refrigerant occurs in each cylinder bore.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a reciprocatory piston type compressoradapted for a refrigeration system of e.g., an automobileair-conditioner. More particularly, it relates to a swash plate-operatedrefrigerant compressor capable of utilizing an injection of arefrigerant gas from a liquid-gas divider o a refrigeration system toenhance compressor discharge performance during the compression ofrefrigerant gas returning from an evaporator of the refrigerationsystem.

2. Related Art

A refrigeration system of an automobile air-conditioner includes arefrigerant compressor such as a fixed capacity swash plate-operateddouble-headed axial piston type compressor and a variable capacity swashplate-operated single-headed axial piston type compressor.

FIG. 6 illustrates a known refrigeration system including an evaporator55, a refrigerant compressor 50 delivering therefrom a high pressure andhigh temperature refrigerant gas by compressing a refrigerant gas whenit returns from the evaporator 55, a condenser 51 for condensing therefrigerant gas after compression when it is sent from the compressor, afirst pressure reducer 52 for reducing a pressure level of the condensedrefrigerant sent from the condenser 51, a liquid-gas divider 53 fordividing the condensed refrigerant into a refrigerant in the gas formand a refrigerant in the liquid form, and a second pressure reducer 54for reducing a pressure level of the refrigerant in the liquid form byintroducing therein from the liquid-gas divider 53. The pressure reducedliquid refrigerant sent from the second pressure reducer 54 is thenevaporated in the evaporator 55 by absorbing heat from an exterior airto thereby cool the air. Namely, the refrigerant compressor 50, thecondenser 51, the first pressure reducer 52, the liquid-gas divider 53,the second pressure reducer 54 and the evaporator 55 are sequentiallyconnected by refrigerant conduits to form a closed refrigeration system.Further, the refrigerant compressor 50 is connected to the liquid-gasdivider 53 by a refrigerant conduit 56 to introduce the dividedrefrigerant gas at a relatively high pressure from the liquid-gasdivider 53 into the compressor 50. Namely, the high pressure refrigerantgas is injected from the divider 53 into the compressor 50 through therefrigerant conduit 56. The injection of the high pressure refrigerantgas can enhance the discharge performance of the compressor to therebyimprove the refrigeration efficiency of the refrigeration system.

The Japanese Unexamined (Kokai) Patent Publication No. 62-175557discloses a typical construction of the swash plate type refrigerantcompressor capable of receiving an injection of the high pressurerefrigerant gas from the liquid-gas divider. In accordance with thecompressor construction of the above-mentioned Patent Publication No.'557, a cylinder block of the compressor is provided with a plurality ofcylinder bores, and a suction chamber fluidly communicated with thecylinder bores via suction valves. The suction chamber has a subsidiarychamber capable of communicating with a particular one of the pluralityof cylinder bores and a main suction chamber capable of communicatingwith the cylinder bores other than the particular cylinder bore. Thesubsidiary suction chamber is provided with an inlet port connected toan injection conduit so as to receive a high pressure refrigerant gasfrom the liquid-gas divider. Therefore, the high pressure refrigerantgas is injected from the subsidiary suction chamber into the particularcylinder bore.

Nevertheless, in the above-mentioned compressor of the JapaneseUnexamined Patent Publication No. 62-175557, the injection of the highpressure refrigerant gas is given to only one of the plurality ofcylinder bores, and accordingly enhancement of the overall dischargeperformance of the compressor must be limited, and therefore theinjection of a high pressure refrigerant gas cannot satisfactorilycontribute to an enhancement of the compressor discharge performance.

Further, if an amount of the injection of the high pressure refrigerantgas is increased to enhance the compressor discharge performance, theparticular single cylinder bore to which the injection of the highpressure refrigerant gas is applied must be constantly subjected to ahigh pressure, and therefore such high pressure acts on a dischargevalve of the particular cylinder bore to thereby reduce physicaldurability thereof.

Furthermore, in the case of the refrigerant compressors such as a vanetype compressor, a rotary type compressor and a scroll type compressor,it is easy to meet structural requirements for receiving an injection ofa high pressure refrigerant gas by employing a relatively simple changein the construction thereto.

Nevertheless, in the case of the reciprocatory piston type compressor, avery complicated construction must be provided for receiving aninjection of a high pressure refrigerant gas into each of the pluralityof cylinder bores.

SUMMARY OF THE INVENTION

An object of the present invention is therefore to provide areciprocatory piston type refrigerant compressor capable of enhancingthe discharge performance thereof by receiving an injection of a highpressure refrigerant gas whereby an increase in the refrigerationefficiency of a refrigeration system in which the compressor isincorporated can be achieved.

In accordance with the present invention, there is provided areciprocatory piston type refrigerant compressor to be incorporated in arefrigeration system provided with a condenser condensing a refrigerant,a first pressure reducer reducing a pressure level of the refrigerantcondensed by the condenser, a liquid-gas divider diving the refrigerantdepressurized by the first pressure reducer into a liquid refrigerantand a refrigerant gas, a second pressure reducer reducing a pressurelevel of the liquid refrigerant supplied from the liquid-gas divider, anevaporator for evaporating the refrigerant gas depressurized liquidrefrigerant, and a refrigerant conduit line for supplying therefrigerant gas from the liquid-gas divider toward the compressor. Thecompressor is characterized by comprising:

an axially extended cylinder block having a central axis thereof, acentral bore extended coaxial with the central axis, and a plurality ofaxial cylinder bores arranged around the central axis to be parallelwith the central axis of the cylinder block; each axial cylinder borehaving first and second opposite ends thereof;

front and rear housings air-tightly connected to opposite axial ends ofthe axially extended cylinder block for defining a suction chamber forthe refrigerant before compression, and a discharge chamber for therefrigerant after compression;

a rotatable drive shaft having axial ends thereof rotatably supported bybearings seated in the front housing and the central bore of thecylinder block;

a plurality of reciprocatory pistons fitted in the plurality of axialcylinder bores of the axially extended cylinder block; each piston beingslid from the first to second end of one of the plurality of cylinderbores for drawing the refrigerant before compression, and from thesecond to first end of the same cylinder bore for compressing the drawnrefrigerant gas;

a swash plate-operated piston drive mechanism arranged around the driveshaft to be cooperative with the drive shaft for reciprocating theplurality of reciprocatory pistons in the plurality of cylinder boreswhen the drive shaft is rotated;

first means for providing a constant refrigerant conduit introducing therefrigerant gas supplied from the liquid-gas divider of therefrigeration system into a definite part of the central bore of thecylinder block; and

second means for successively creating a radial fluid communicationpassageway means between the definite part of the central bore of thecylinder block and each of the plurality of cylinder bores at a portionadjacent to the first end thereof in response to the rotation of thedrive shaft, the radial fluid communication passageway means permittingan injection of the refrigerant gas from the definite part of thecentral bore into the portion of each cylinder bore adjacent to thefirst end thereof when the piston is at a compression stroke thereof.

The second means may comprise a plurality of radial passageways fixedlyformed in the cylinder block to provide a constant communication betweenthe central bore and the plurality of cylinder bores of the cylinderblock, and a rotary valve element arranged in the central bore of thecylinder block so as to be rotatable together with the drive shaft; therotary valve element having an end face provided with a single radialpassageway recessed in the end face to form a definite part of thecentral bore; the single radial passageway of the rotary valve elementcapable of coming into radial alignment with one of the plurality ofradial passageways of the cylinder block in response to the rotation ofthe rotary valve element.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be made apparent from the ensuing description ofpreferred embodiments thereof in conjunction with the accompanyingdrawings wherein:

FIG. 1 is a longitudinal cross-sectional view of a variable capacityswash plate type compressor in accordance with an embodiment of thepresent invention;

FIG. 2 is a perspective view of a rotary valve element accommodated inthe compressor of FIG. 1, illustrating a key way and an axial holeformed in one end face thereof;

FIG. 3 is another perspective view of the same rotary valve element asthat of FIG. 2, illustrating a radial passageway recessed in the otherend face thereof;

FIG. 4 is an end view of the cylinder block of the compressor of FIG. 1,illustrating an arrangement of cylinder bores and radial passagewaysprovided therein;

FIG. 5 is an explanatory diagram indicating a timing for carrying out aninjection of a high pressure refrigerant gas into each cylinder bore;and,

FIG. 6 is a schematic circuit diagram illustrating a refrigerationsystem in which a compressor capable of receiving an injection of a highpressure refrigerant gas is incorporated.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a swash plate-operated reciprocatory piston typecompressor includes an axial cylinder block 1 having a central axis,opposite axial ends, a central bore la extended coaxially with thecentral axis, and a plurality of (five) cylinder bores 1b arrangedequiangularly around and in parallel with the central axis. One of theaxial ends, i.e., a front end of the cylinder block 1 is air-tightlyclosed by a front housing 2, and the other end, i.e., a rear end of thecylinder block is air-tightly closed by a rear housing 4 via a valveplate 3. The front housing 2 defines a crank chamber 5 axially extendingin front of the front end of the cylinder block 1. The rear housing 4defines therein a suction chamber 17 for a refrigerant beforecompression and a discharge chamber 18 for a refrigerant aftercompression therein.

A drive shaft 6 axially extending through the crank chamber 5 isrotatably supported by bearings seated in a central bore of the fronthousing 2 and the central bore 1a of the cylinder block 1. The driveshaft 6 has a rotor 7 fixedly mounted thereon to be rotated together andaxially supported by a thrust bearing 7a arranged between an inner endof the front housing 2 and the frontmost end of the rotor 7. The rotor 7has a support arm 8 extending from a rear part thereof to provide anextension in which an elongated through-bore 8a is formed for receivinga lateral pin 8b slidably movable in the through-bore 8a. The lateralpin 8b is connected to a swash plate 9 arranged around the drive shaftso as to be able to change an angle of inclination thereof with respectto a plane perpendicular to the rotating axis of the drive shaft 6.

A sleeve element 10 axially slidably mounted on the drive shaft 6 isarranged adjacent to the rearmost end of the rotor 7, and is constantlyurged toward the rearmost end of the rotor 7 by a coil spring 11arranged around the drive shaft 6 at a rear portion thereof. The sleeveelement 10 has a pair of laterally extending trunnion pins 10a on whichthe swash plate 9 is pivoted so as to be inclined thereabout.

The swash plate 9 has an annular rear face and a cylindrical flange tosupport thereon a non-rotatable wobble plate 12 via a thrust bearing 9a.The nonrotatable wobble plate 12 has an outer periphery provided with aguide portion 12a in which a long bolt 16 is fitted to prevent anyrotational play of the wobble plate 12 on the swash plate 9, and thewobble plate 12 is operatively connected to pistons 15 axially slidablyfitted in the cylinder bores 1b, via connecting rods 14. When the driveshaft 6 is rotated together with the rotor 7 and the swash plate 9, thewobble plate 12 on the swash plate 9 is non-rotatably wobbled to causereciprocation of respective pistons 15 in the cylinder bores 1b. Inresponse to the reciprocation of the pistons 15, the refrigerant isdrawn from the suction chamber 17 into respective cylinder bores 1b andcompressed therein. The compressed refrigerant is discharged fromrespective cylinder bores 1b toward the discharge chamber 18 from whichthe refrigerant after compression is delivered to the condenser of arefrigeration system.

During the operation of the compressor, when there appears a change in apressure differential between a suction pressure in each cylinder borelb and a pressure prevailing in the crank chamber 5, the stroke of eachpiston 15 is changed, and therefore, the angle of inclination of theswash plate 9 and the wobble plate 12 is changed. The pressure in thecrank chamber 5 is adjustably changed by a conventional solenoid controlvalve (not shown in FIG. 1) housed in an extended portion of the rearhousing 4.

The rear housing 4 having the afore-mentioned suction and dischargechambers 17 and 18 therein is provided with a fluid conduit 20 in theform of a through-bore centrally formed therein to fluidly communicatewith the central bore la of the cylinder block 1 via a central bore 3aof the valve plate 3. The fluid conduit 20 has an inlet opening formedin the rear end face of the rear housing 4 to introduce a refrigerantgas at a high pressure from a liquid-gas divider of the refrigerationsystem into the compressor via the fluid conduit 20. Namely, the highpressure refrigerant gas introduced through the fluid conduit 20 isinjected into respective cylinder bores 1b in a manner that will bedescribed later.

The cylinder block 1 is provided with radial injection passageways 21formed therein to provide communication between the central bore 1a andeach of the cylinder bores 1b. Each of the radial injection passageways21 opens into each cylinder bore 1b at a rear end portion of thatcylinder bore 1b where the piston 15 approaches to the top dead centerthereof,

Further, a rotary valve element 22 in the cylinder form is rotatablyarranged in the central bore 1a of the cylinder block 1 and fixedlykeyed by a key 23 to an end portion of the drive shaft 6 extended intothe central bore 1a. The rotary valve element 22 is axially constantlyurged against an inner face of the valve plate 3 by a coil spring 25arranged between an end of the rotary valve element 22 and a step-likespring seat of the drive shaft 6.

As best shown in FIGS. 2 and 3, one of the opposite end faces of therotary valve element 22 is provided with a central bore 22c formedtherein to be engaged with the end of the drive shaft 6 and a key groove22a for receiving the above-mentioned key 23, and the other end face ofthe rotary valve element 22 is provided with a radial fluid passageway22b recessed therein to extend from the center to the periphery. Theradial fluid passageway 22b of the rotary valve element 22 is arrangedto successively come into radial registration with each of the injectionpassageways 21 of the cylinder block 1 when the rotary valve element 22is rotated together with the drive shaft 6 in a direction "a" shown inFIG. 4. Moreover, the rotary valve element 22 is fixed to the driveshaft 6 in such a manner that the above-mentioned radial registration ofthe fluid passageway 22b of the rotary valve element 22 with each of theinjection passageways 21 of the cylinder block 1 occurs at apredetermined time when each of the pistons 15 is advanced from thebottom dead center thereof to a selected position before the top deadcenter thereof P in the cylinder bore 1b during the compression strokethereof. As shown in FIG. 5, the positional discrepancy between theabove-mentioned selected position and the top dead center of the piston15 corresponds to an angular amount "θ" in relation to the rotation ofthe rotary valve element 22. Namely, the angular amount "θ" is chosen sothat an injection of the refrigerant gas at high pressure appropriatelyoccurs from the central bore 1a into each cylinder bore 1b in which thepiston 15 proceeds from the bottom to top dead center thereof forcarrying out compression of the refrigerant, via the fluid passageway22b of the rotary valve element 22 and the injection passageway 21 ofthe cylinder block 1.

The above-described reciprocatory piston type compressor is incorporatedin a refrigerating circuit of a refrigeration system similar to thatshown in FIG. 6; the system of which performs an air refrigerationoperation when used with an air-conditioner such as an automobileair-conditioner. Thus, the suction chamber 17 of the compressor isconnected to an evaporator such as the evaporator 55, the dischargechamber 18 is connected to a condenser such as the condenser 51, and thefluid conduit 20 is connected to a liquid-gas divider such as theliquid-gas divider 53 via a refrigerant conduit.

The operation of the reciprocatory piston type compressor of FIG. 1 isdescribed hereinbelow with reference to FIGS. 1 and 6.

When the compressor is driven so that the drive shaft 6 is rotated, theswash plate 9 is rotated together with the drive shaft 6 to perform awobbling motion thereof, and accordingly the wobble plate 12 isnon-rotatively wobbled to cause reciprocation of the pistons 15 in therespective cylinder bores 1b. Thus, in response to the reciprocation ofthe respective pistons 15, the refrigerant is drawn in the respectivecylinder bores 1b from the suction chamber 17, compressed therein, anddischarged therefrom toward the discharge chamber 18 of the rear housing4.

The rotation of the drive shaft 6 rotates the rotary valve element 22,and therefore the fluid passageway 22b of the rotary valve element 22successively comes into registration with one of the injectionpassageways 21 in a manner so that a fluid communication is createdbetween the fluid conduit 20 and the cylinder bore lb in which thepiston 15 carries out the compression stroke thereof for a certain timeinterval, via the registered fluid and injection passageways 22b and 21,and a portion of the central bore 1a of the cylinder block 1. Therefore,the refrigerant gas at high pressure introduced from the liquid-gasdivider 53 into the fluid conduit 20 of the compressor is injected intothe cylinder bore 1b, in which the piston 15 performs the compressionstroke thereof. Namely, an injection of the refrigerant gas is made toincrease the pressure level within the injected cylinder bore 1b.

When the rotary valve element 22 is rotated to a subsequent position atwhich the fluid passageway 22b of the rotary valve element 22 comes intoradial registration with the subsequent injection passageway 21 openingtoward the cylinder bore 1b next to the cylinder bore lb to which theinjection of the refrigerant gas was applied, the injection of the highpressure refrigerant gas is similarly made to that subsequent cylinderbore 1b during the compression stroke. Accordingly, the rotation of therotary valve element 22 eventually applies an equal injection of therefrigerant gas to every cylinder bore 1b at a predetermined time closeto the termination of the compression stroke of that cylinder bore 1b.

The injection of the high pressure refrigerant gas made equally to everycylinder bore 1b of the compressor can improve total compressionperformance of the compressor, and accordingly the ability of thecompressor to discharge the compressed refrigerant gas toward therefrigeration system is significantly enhanced. Further, the utilizationof the refrigerant gas divided by the liquid-gas divider of therefrigeration system for the injection of the high pressure refrigerantgas into every cylinder bore of the multi-cylinder reciprocatory pistontype compressor can increase the operational efficiency of therefrigeration system.

From the foregoing description, it should be understood that inaccordance with the present invention a gas injection type refrigerantcompressor capable of being incorporated in a refrigeration system canbe constructed because of the provision of a simple valve element, i.e.,the rotary valve element 22 without a cumbersome change in the internalconstruction of the conventional reciprocatory piston typemulti-cylinder compressor.

Further, in the described embodiment of the present invention, thereciprocatory piston type compressor is provided with a plurality ofsingle-headed pistons reciprocated by a wobble plate typerotation-to-linear motion converter. Nevertheless, it should beunderstood that the present invention will be equally applicable to afixed inclination swash plate type compressor in which a plurality ofdouble-headed pistons are reciprocated in a plurality of pairs of frontand rear cylinder bores arranged on both sides of a swash plate chamberof a cylinder block, in which a fixed inclination swash plate is rotatedtogether with an axial drive shaft. In the fixed inclination swash platetype compressor, the front and rear cylinder bores must be provided withrespective front and rear rotary valve elements and front and rearinjection passageways in a symmetrical arrangement so as to permit theinjection of a high pressure refrigerant gas into these front and rearcylinder bores during the alternate compression stroke s of respectivedouble-headed pistons. Namely, the compression stroke in each frontcylinder bore and that in each rear cylinder bore occur to be out ofphase with one another by an angle of 180 degrees during one revolutionof the drive shaft. Therefore, it is necessary for the front and rearrotary valve elements to be attached to the opposite ends of the driveshaft so that the injection of the refrigerant gas to the front cylinderbore occurs 180 degrees in advance or behind the injection of therefrigerant gas to the rear cylinder bore.

It should be understood that further modifications and variations of thepresent invention will occur to persons skilled in the art withoutdeparting from the scope and sprit of the invention as claimed in theappended claims.

We claim:
 1. A reciprocatory piston type refrigerant compressor to beincorporated in a refrigeration system provided with a condensercondensing a refrigerant, a first pressure reducer reducing a pressurelevel of the refrigerant condensed by the condenser, a liquid-gasdivider diving the refrigerant depressurized by the first pressurereducer into a liquid refrigerant and a refrigerant gas, a secondpressure reducer reducing a pressure level of the liquid refrigerantsupplied from the liquid-gas divider, an evaporator for evaporating therefrigerant gas depressurized liquid refrigerant, and a refrigerantconduit line for supplying the refrigerant gas from the liquid-gasdivider toward the compressor, comprising:an axially extended cylinderblock having a central axis thereof, a central bore extended coaxialwith the central axis, and a plurality of axial cylinder bores arrangedaround the central axis parallel with the central axis of the cylinderblock; each axial cylinder bore having first and second opposite endsthereof; front and rear housings air-tightly connected to opposite axialends of said axially extended cylinder block for defining a suctionchamber for the refrigerant before compression, and a discharge chamberfor the refrigerant after compression; a rotatable drive shaft havingaxial ends thereof rotatably supported by bearings seated in said fronthousing and said central bore of said cylinder block; a plurality ofreciprocatory pistons fitted in said plurality of axial cylinder boresof said axially extended cylinder block; each piston being slid from thefirst to second end of one of said plurality of cylinder bores fordrawing the refrigerant before compression, and from the second to firstend of the same cylinder bore for compressing the drawn refrigerant gas;a swash plate-operated piston drive mechanism arranged around the driveshaft so as to be cooperative with the drive shaft for reciprocatingsaid plurality of reciprocatory pistons in said plurality of cylinderbores when said drive shaft is rotated; first means for providing aconstant refrigerant conduit introducing the refrigerant gas suppliedfrom said liquid-gas divider of said refrigeration system into adefinite part of said central bore of said cylinder block; and secondmeans for successively creating a radial fluid communication passagewaymeans between said definite part of said central bore of said cylinderblock and each of said plurality of cylinder bores at a portion adjacentto the first end thereof in response to the rotation of said driveshaft; said radial fluid communication passageway means permitting aninjection of the refrigerant gas from the definite part of the centralbore into said portion of each cylinder bore adjacent to the first endthereof when said piston is at a compression stroke thereof.
 2. Areciprocatory piston type refrigerant compressor according to claim 1,wherein said second means comprises:a plurality of radial passagewaysfixedly formed in said cylinder block to provide a constantcommunication between said central bore of said cylinder block and saidplurality of cylinder bores, and a rotary valve element arranged in saidcentral bore of said cylinder block to be rotatable together with saiddrive shaft; said rotary valve element having an end face provided witha single radial passageway recessed in said end face to form saiddefinite part of said central bore; said single radial passageway ofsaid rotary valve element capable of successively coming intoregistration with one of said plurality of radial passageways of saidcylinder block in response to the rotation of said rotary valve element.3. A reciprocatory piston type refrigerant compressor according to claim2, wherein said rotary valve element arranged in said central bore ofsaid cylinder block is keyed to said drive shaft so as to be rotatabletogether with said drive shaft.
 4. A reciprocatory piston typerefrigerant compressor according to claim 1, wherein said first meanscomprises an axial through-bore formed in said rear housing; said axialthrough-bore being in communication with said refrigerant conduit lineof said refrigeration system and with said central bore of said cylinderblock.